The present invention relates to a method for the production of steel from sponge metal by using gas plasmas as the energy carrier.
German Pat. No. 2,149,407, corresponding to U.S. Pat. No. 3,843,352, to Klaus-Herbert Ulrich, discloses a method for melting sponge metal by means of gas plasmas in which the sponge-like raw material is introduced from the top into a melting vessel containing a metal bath which has a layer of slag on its top. The sponge metal has a lower density than the slag and therefore floats on the slag. A plasma is directed onto the melt from the top and thereby melts the sponge metal. The melted sponge metal has a greater density than the slag, and accordingly the melted sponge metal then drops through the liquid slag in the form of droplets into the metal bath. Impurities such as sulfur and phosphorus for example, originally contained in the sponge metal are absorbed by the slag. In this method, however, it is necessary to add to the melting vessel slag-forming substances including acidic and basic substances, and their liquefaction requires energy. The method of the present invention intends to overcome this drawback.
German Pat. No. 2,110,274, corresponding to U.S. Pat. No. 3,771,585, to Klaus-Herbert Ulrich, discloses an apparatus for melting sponge metal by means of inert gas plasmas. This process does not involve slag work, but the amount of apparatus required is very high, since the sponge metal must be cleaned under vacuum. The method of the present invention overcomes this drawback as well.